If you study the Crusades and just how bitterly savage and cruel they were, you'd know why the people of the Middle East, and certainly not just the Muslim population, are still bitter about the Crusades.
Here are first and second hand accounts from the First Crusade, of what happened after the Siege of Ma'arra,
"Some people said that, constrained by the lack of food, they boiled pagan adults in cooking-pots, impaled children on spits and devoured them grilled." - Rudolph of Caen, from his chronicle, Gesta Tancredi
"I shudder to tell that many of our people, harassed by the madness of excessive hunger, cut pieces from the buttocks of the Saracens already dead there, which they cooked, but when it was not yet roasted enough by the fire, they devoured it with savage mouth." - Fulcher of Chartres, from his chronicle, Gesta Francorum
"[T]he Christians did not shrink from eating not only killed Turks or Saracens, but even creeping dogs..." - Albert of Aix, from his Historia
These are the accounts of Christians who participated in the First Crusade, who either witnessed these things for themselves or were aware of these horrors.
There's a reason why the Crusades bring bitter memories to the people of the Middle East. As the Crusades involved the slaughter of innocents, men, women, children, animals; Muslims, Jews, Samaritans, and even other Christians were all victims of the Crusades.
-CryptoLutheran